The series is based on ‘Let This Be Our Secret’, a book by former journalist Deric Henderson which tells the story of how the Ballymoney dentist and lay preacher gassed his wife Lesley and Stewart’s husband Trevor Buchanan - and made their deaths look like a suicide pact.

Written by Bafta winning writer Stuart Urban (An Ungentlemanly Act), the drama is directed by Nick Murphy (Occupation, Prey) and produced by Jonathan Curling (Holy Cross, The Government Inspector)